The present invention relates to an improved well point of the type employed to de-water subsurface excavations.
Well points of the type to which this invention relates are exemplified in U.S. Pat. Nos. 1,915,136 issued Jun. 20, 1933, 2,027,398 issued Jan. 14, 1936 and 2,388,640 issued Nov. 6, 1945, which patents give excellent disclosures of the manner in which such a well point is used.
Applicant's own prior U.S. Pat. No. 2,835,328 issued May 20, 1958 is also directed to a well point designed to facilitate the rapid extraction of water from subsurface formations. The well point disclosed in this patent included a tube of rectangular cross-section having external interrupted screw threads on its corners adjacent one end, an internally screw threaded coupling socket fixed to the tube and extending longitudinally from the end thereof remote from the threads, an annular flange carried by the socket and extending therefrom toward the threaded end of the tube in spaced relation to the tube, a tubular screen encircling the tube and extending into the space between the tube and the flange, an earth penetrating tip threadedly engaged with the tube for engaging the screen and removably holding it in place on the tube, said tip having a liquid discharge chamber therein which establishes communication between the interior of the screen and the exterior of the tube. A spacer rod is secured to each side of the tube for engaging the screen and preventing its collapse under external pressure with opposite ends of the spacer rod diverging from the tube as they approach the end thereof for yieldingly engaging the screen and assuring a sand-tight connection with the socket and the tip.
While the above described well point performed well under certain circumstances, there was a tendency for the screen to become clogged in some types of soil and to be deformed under pressure with a resultant separation of the screen from the socket and/or the tip. Further, the restricted space between the lower end of the tube and the tip where the tube is threadedly engaged with the tip unduly restricted the flow of water into the discharge chamber when suction was applied to the tube. Finally, the foregoing construction of all metallic parts was expensive to build, time consuming to assemble and rather heavy and cumbersome to handle.